DESCRIPTION: In a randomized controlled trial, with 6-month and 1-year follow-up, this application aims to evaluate whether the Harnessing Online Peer Education (HOPE) social media intervention can be used to increase HIV self- testing among African American and Latino men who have sex with men (MSM), and to analyze the changing social network characteristics of participants in this intervention. Innovative approaches to HIV prevention and treatment are critical in the attempt to control the spread of HIV, especially among African American and Latino men who have sex with men (MSM), who are at the highest risk for HIV. Community-based HIV prevention strategies, such as peer leader diffusion models, have been successful in spreading HIV-risk behavior reductions, but require time and economic resources. With the recent increase in social media usage among African American and Latino MSM, social media and online social networks such as Facebook might be used to efficiently and cost-effectively deliver evidenced-based, peer-led HIV prevention interventions. Advances in testing technology, such as home-based HIV testing, can be integrated into an online HIV prevention intervention to allow participants to anonymously test for HIV without risking the stigmatization associated with in-person testing. Because social networking interventions provide rich data on social network characteristics (e.g., the number of friends participants make over time, content of health communication within online networks), this information can be recorded and used to improve intervention delivery. Results from our Los Angeles HOPE pilot study have already demonstrated a) the feasibility and acceptability of using social networking technologies to deliver peer-led HIV prevention among African American and Latino MSM, b) interest in home-based HIV testing among these populations, and c) the relationship between social network dynamics and HIV prevention behavior change. However, additional research is needed with a larger sample to determine the large-scale effectiveness of using social media to increase HIV testing and linkage to care among African American and Latino MSM. In this study, HIV negative African-American and Latino MSM will be invited to join an online (private) Facebook group related to HIV prevention and interact with peer leaders trained in HIV prevention over 12 weeks, with 6-month and 1-year follow-up. Compared to control group participants receiving 12 weeks of peer- delivered general health information over Facebook groups, we predict that participants receiving 12 weeks of peer-delivered HIV prevention information will be more likely to take a home-based HIV test. We will also measure participants' social network data to assess the relationship between changing social network dynamics (e.g., density, network size) and intervention effects.